The supernova is more comfortable in my opinion because the rims are much less sharp and flatter. It feels lighter through combos as well. the burnside is smoother and quieter on the string and on grinds.
I say get a Square Wheels royale. Although I haven’t played it I’ve heard it’s super comfy in the hand and is just an all around great yoyo.
But out of the yoyos you said above, get the Supernova as I found it slightly more comfortable in the hand than the burnside, but if you want a better player get the burnside.
If you want comfy, Supernova
If you want player, Burnside
If you want both, Royaleeeee.